1. Field of the Invention
The present invention relates to a media transmission method and apparatus for a network. More particularly, the present invention relates to a media transmission method and apparatus which can reduce transmission quality degradation and transmission delay which occur because media is being transmitted through an exchange system.
2. Description of the Related Art
Early networks were classified into a voice network through which voice was transmitted and a data network through which data was transmitted. That is, voice was transmitted via the voice network, such as a Public Switched Telephone Network (PSTN), and data was transmitted via the data network, such as an IP network. However, in line with the ongoing development of network technology, the data network is being incorporated into the voice network, so that many present-day networks can transmit voice via the data network. Moreover, some present-day networks can transmit media containing video as well as voice. Voice over Internet Protocol (VoIP) technology is a representative technology employed to transmit voice via a data network, wherein voice in packetized form is transmitted over an IP network. The VoIP technology performs session setting and information exchange for transmitting voice by a signaling procedure, and transmits voice via the exchanged information during the set session.
A network includes an exchange system, a proxy server, and an IP network. Terminals A and B exchange voice via the network. The exchange system is an exchange system which has an integration function for exchanging both voice and data. Hereinafter, the term exchange system is used to refer to an exchange system which has such an integration function, unless otherwise stated.
Voice over Internet Protocol (VoIP) technology separately runs a media control function and a media transmission function.
Signaling is performed by the proxy server, which performs a function for initializing access to a receiving party instead of an originating party. Some terminals can directly call the opposite terminal without going through the proxy server.
A signal processor performs signaling for voice transmission, and a media processor and an Ethernet switch perform voice transmission after signaling. However, the terminals A and B connected to the exchange system cannot directly transmit data to each other even after signaling ends. This is because the terminal A cannot obtain information about the terminal B that it desires to communicate with. Information obtained by the terminals A and B after signaling is information of the exchange system rather than information of the opposite terminal. Therefore, there can be a case where an independent protocol, other than a standard protocol, is used between the terminal A and the exchange system. As a result, the terminals A and B must transmit voice to each other via the exchange system. That is, the terminal A can transmit voice to the terminal B by first transmitting voice to the exchange system which then relays the voice to the terminal B. Likewise, voice to be transmitted from the terminal B to the terminal A is transmitted to the terminal A via the exchange system.
That is, voice transmission between the terminals A and B must be performed via the media processor of the exchange system. However, the media processor must perform data transformation for the voice transmission. Voice transmitted between the terminals A and B via the media processor must undergo transformation from a voice packet to a Pulse Code Modulation (PCM) voice signal and from the PCM voice signal to the voice packet. Such data transformation causes degradation of voice quality and transmission delay. In addition, the media processor of the exchange system uses an unnecessary voice compression codec, leading to an overuse of resources. Such problems occur in the transmission of other media such as video, as well as voice.